Rotary compressor with unloading impeller



Jan. 2-, 1968 J. w. JACOBS 3,361,342

ROTARY COMPRESSOR WITH UNLOADING IMPELLER I Filed Jan. 6, 1967 2 Sheets-Sheet l INVENTOR.

ATTORNEY Jan. 2, 1968 J. w. JACOBS 3 3 v ROTARY COMPRESSOR WITH UNLOADING IMPELLER Filed Jan. 6, 1967 2 Sheets-Sheet 2 INVENTOR.

ATTORNEY United States Patent f 3,361,342 ROTARY COMPRESSOR WITH UNLOADING IMPELLER James W. Jacobs, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Jan. 6, 1967, Ser. No. 607,837 2 Claims. (Cl. 230138) ABSTRACT OF THE DISCLOSURE This eccentric type rotary compressor has an eccentric impeller which is moved by centrifugal force to a position of maximum eccentricity. The eccentric impeller is rotatably mounted upon a rotatable eccentric shaft. When the eccentric shaft slows down and reduces the centrifugal force upon it this eccentric impeller is moved by frictional drag to a position of reduced eccentricity for unloading the compressor.

This invention pertains to the unloading of eccentric type rotary compressors at the end of each running period.

The advantages of unloading a compressor at the start of each running period has been known for many years. However, unloading devices have been sufliciently troublesome that most manufacturers avoid placing them in a sealed motor compressor unit.

It is an object of this invention to make the impeller of an eccentric rotary type compressor centrifugally responsive so that upon approaching maximum speed it will move to a position of maximum eccentricity for maximum pumping and when the speed and centrifugal force is reduced it will move to lesser eccentricity to unload the compressor in preparation for the next start.

This and other objects are attained in the form shown in the drawings in which the first form of impeller is eccentric in shape and is rotatably mounted upon an eccentrically rotatable drive shaft and moved by centrifugal force to a position of maximum eccentricity and upon reduction in speed and centrifugal force is moved by frictional drag to a position of lesser eccentricity for unloading the compressor. In the second form of impeller, a roller is rotatably mounted upon the eccentric impeller member and the two operate together in amanner similar to the first impeller.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a fragmentary vertical sectional view through a sealed rotary eccentric type motor compressor unit embodying one form of my invention with the impeller shown in a position of maximum eccentricity;

FIGURE 2 is a fragmentary vertical sectional view similar to FIGURE 1 with the impeller shown in a position of reduced eccentricity;

FIGURE 3 is a horizontal sectional view taken along the line 3-3 of FIGURE 2 with the impeller shown in the position of maximum eccentricity;

FIGURE 4 is a fragmentary vertical sectional view through the second form of the invention with the impeller shown in the position of maximum eccentricity; and

FIGURE 5 is a fragmentary vertical sectional view similar to FIGURE 4 but with the impeller shown in the position of minimum eccentricity.

Referring now more particularly to FIGURE 1, there 3,361,342 Patented Jan. 2, 1968 is shown a sealed motor compressor unit which is generally similar to that shown in Patent 3,016,183 issued January 9, 1962, which may be referred to for illustration of the remaining parts of the compressor which are not disclosed herein. As shown herein there is illustrated an electric motor stator 20 supported by the frame 22 which also provides a centrally located bearing 24 within which is located the rotatably mounted drive shaft 26. The drive shaft 26 is connected to the motor rotor (not shown) located within the stator 20. Beneath the bearing 24 a cylinder 28 and a bottom plate 30 are fastened by screws 31 to the frame 22 to enclose a flat cylindrical compression chamber 32. The drive shaft 26 has an eccentric shaft 34 extending within the compression chamber and extending from this eccentric portion 34 is a short bearing portion 36 rotatably mounted in the bottom plate 30.

In the aforesaid patent a cylindrical rotor is rotatably mounted upon the eccentric portion 34. A divider block 33 slides in the cylinder 28 and is yieldingly held in contact.

According to this invention, an eccentric roller 38 is rotatably mounted upon the eccentric shaft portion 34 and is provided with an eccentricity or throw which is approximately equal to the eccentricity or throw of the shaft porton 34 relative to the shaft 26. Its diameter and eccentricity or throw must be sufiicient with the aid of the lubricant to come substantially into sealing relation with the inner cylindrical wall 40 of the cylindrical compression chamber 32 when its axis of maximum eccentricity or throw is aligned with the eccentric position or throw of the eccentric shaft portion 34 in additive rela tion as shown in FIGURES 1 and 3. A divider block 33 is slidably mounted int he cylinder wall 28 and is yieldingly held in contact with the periphery of the impeller 38 to separate the inlet 42 from the outlet 44.

The eccentric impeller 38 is freely rotatable upon the eccentric shaft portion 34 so that when the shaft 26 is rotated at maximum speed the centrifugal force will move the eccentric impeller member 38 into its position of maximum eccentricity with its throw aligned with the throw of the eccentric shaft portion 34 in additive relation for maximum pumping capacity and for making substantial sealing relation with the cylindrical wall surface 40 as it sweeps around the compression chamber 32 and moves the gas from the inlet port 42 to the outlet port 44. Lubrication is provided by the reservoir of lubricant 46 which is held in the bottom of the sealed casing 48 surrounding the walls of the compression chamber 32 and carried into the compression chamber through lubricating grooves 50 provided in the various portions of the shaft 26.

When the sealed motor compressor unit is deenergized and the rotation of the shaft 26 slows down, the centrifugal force upon the impeller 38 will diminish rapidly so that the frictional drag of the lubricant upon the walls of the compression chamber 32 will cause the impeller 38 to drag behind the position of maximum eccentricity to move its throw out of alignment with the throw of the eccentric shaft portion 34 to unseal the impeller 38 from the walls thereof so that the compressor will be unloaded in preparation for the next start thereof.

In the form shown in FIGURES 4 and 5 the construction of all of the parts excepting the impeller is the same. In this form, however, the impeller includes an inner eccentric portion 121 which is rotatably mounted upon the eccentric shaft portion 34 and has an eccentricity or throw which is similar in amount to the eccentricity or throw of the shaft portion 34 relative to the shaft 26. Rotatably mounted upon the periphery of the inner eccentric member 121 is a cylindrical roller 123 which is sufiicient in thickness with the aid of the lubricant to make sealing relation with the inner walls 40 of the compression chamber 32 when the maximum eccentricity of the inner eccentric member 121 is added to the eccentricity of the eccentric shaft portion 34.

The operation of the second form is similar to that of the first form. When the speed of the shaft 26 and the centrifugal force upon the eccentric 121 and the roller 123 reaches a maximum, the eccentric 121 will move so that both throws are aligned and its maximum eccentricity adds to the maximum eccentricity of the eccentric shaft portion 34 to cause the roller to make sealing relation with the walls 40 to cause the combined impellers 121, 123 to move the gas from the inlet to the outlet for pumping at maximum efliciency. When the sealed motor compressor is deenergized and the speed of the shaft 26 and the centrifugal force diminishes, the frictional drag upon the roller 123 and the eccentric 121 will cause the throw of the eccentric member 121 'andthe roller 123 to lag behind the throw of the eccentric shaft portion 34 and move out of sealing engagement with the walls 40 to unload the compressor in preparation for the next start thereof.

Thus, I have provided a very simple automatic unloading arrangement for an eccentric type rotary compressor.

While the embodiments of the invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A compressor including rotatable driving means having an inner rotatable eccentric portion including a throw, a cylinder having an inner peripheral wall surrounding said eccentric portion containing a compression chamber and an inlet and an outlet, sealing means separating the inlet and outlet, wherein the improvement comprises rotatably mounting upon said inner eccentric portion a loading and unloading means coperating with said sealing means and said wall including an eccentric impeller rotatably mounted on said inner eccentric portion having a throw subject to high centrifugal force acting to place its throw in alignment with the throw of said inner rotatable eccentric portion in additive relation for achieving maximum eccentricity at maximum speeds of rotation for substantial sealing relation with said wall to load the compressor and responsive to frictional drag at lower speeds for moving the throw of said eccentric impeller out of alignment with the throw of said inner rotatable eccentric portion to reduce the eccentricity for retracting said impeller out of sealing relation with said wall to unload the compressor, the diameters and throws of said eccentric portion and said eccentric impeller only when their throws are substantially aligned inadditive relation being sufficient to extend the periphery of said impeller into substantial sealing relation with said inner peripheral wall for loading the compressor.

2. A compressor as defined in claim 1 in which said eccentric impeller comprises -a symmetrical roller and an eccentric rotatably mounted within said roller and rotatably mounted upon said inner rotatable eccentric portion.

References Cited UNITED STATES PATENTS 1,685,397 9/1928 Carrey 230- 7 3,016,183 1/1962 Murphy et al. 230139 FOREIGN PATENTS 556,217 8/1932 Germany. 350,071 6/1931 Great Britain.

DONLEY J. STOCKING, Primary Examiner.

WILBUR I. GOODLIN, Examiner. 

